1. Field
The present disclosure relates generally to aircraft components and in particular to thermally activated variable stiffness composite materials used in aircraft components. Still more particularly, the present disclosure relates to a method and apparatus for using thermally activated variable stiffness composite materials in seals for aircraft.
2. Background
In aircraft, a folding wing is a design feature that may be used to save space. For example, naval based aircraft that operate from limited deck space on an aircraft carrier may have folding wings to reduce the amount of space occupied by the aircraft. A folding wing allows an aircraft to occupy less space in a confined hangar because the folded wing normally rises over the fuselage.
This folded configuration decreases the floor area occupied by the aircraft. In some cases, vertical clearance may be limited on hangar decks in an aircraft carrier. With this type of limit, some aircraft may have additional hinges to fold the wing tips downwards.
With folding wings, seals may be present at any movable joint with a gap. A seal may provide a capability to cover the chord-wise seam between inboard and outboard wing sections and prevent gap formation between the seal and out-board wing section when the wings are in an unfolded condition. Further, the seals may allow for maintaining a continuous surface when the wing is in an unfolded condition to provide better aerodynamic performance.
Currently available seals used in aircraft may use a graded thickness graphite reinforced fiber polymer composite flap that overlaps a seam between the inboard and outboard wing structures. Preloading this “knife” seal against the opposing wing surface helps prevent gap formation during in-flight air aero loads and wing deflections during maneuvers. The thinner flexible portion of the knife-edge of the seal may accommodate wing deflections during maneuvers.
Additionally, this type of seal also may permit electrical conductivity and impedance continuity across the gap for low observable properties. Further, with this type of seal, the thin knife-edge of the flap is compliant to permit sufficient deflection needed for wing folding.
These requirements may change along the chord length of the wing as a result of factors such as, for example, wing curvature, hinge mechanism, design aerodynamic continuity, and electrical continuity. The contradictory stiffness and deformation requirements may be difficult to balance in a manner that prevents physical gap formation and allows for electrical continuity in the seal.
Therefore, it would be desirable to have a method and apparatus that overcomes the problems described above.